Development Tools/Demo Boards - MCP3903 Evaluation Board Connections - Input Voltage Range
Consider the MCP3913 unless the system requires a 5 V rail (3913 is 3 V only).
Some have used an external through-hole resistor, screwed it into one of the terminals on the left-hand side of the board to create a voltage divider of 1000:1 (with the low side of the voltage divider being one of the surface-mount parts on the board). They put the desired voltage (e.g., 210 V) on the resistor (the side not screwed in, which is off the board), then the divider gives a 210 mV AC signal on the board going into the device.
The voltages on the board going directly into the 3903 must be within the limits of the 3903 input range, which is +/-500 mV.